In order to detect an object falling onto a transport track, for example, in an underground railway station, it is known to use a video camera which is positioned above the tracks. However, this solution is not completely satisfactory because it requires extensive and expensive installation and maintenance operations and does not function correctly if the viewing angle of the camera is obscured.
Another known solution is to provide a plurality of electroluminescent diodes along the transport track, for example, one diode every 25 cm. The diodes emit beam rays, and it is possible to detect an interruption of the beam rays. That solution requires a large number of diodes and detectors which also involves extensive and expensive installation and maintenance operations.